The present invention relates to water heater devices and more particularly to a thermally insulated water heater device. It is becoming more important to improve the insulation of hot water heaters to conserve energy, and the present invention is directed to improve insulation concepts.
Typically, water heater devices are constructed of an inner water tank with an outer shell located concentrically over the inner tank defining an annular space therebetween, a cap closing the top end of the water heater device, and a floor closing the bottom end of the water heater device. The space between the inner tank and outer shell is filled with a thermal insulation. For many years fiberglass mats have been used as the insulation material between the inner tank and outer shell. More recently a foam, such as urethane, has been used as the thermal insulation material in place of fiberglass between the inner tank and outer shell. Typically, a foamable material is injected into the annular space between the inner tank and outer shell, and is allowed to foam in situ. However, there is a problem in restraining the expanding foam within the annular space and more particularly within a predetermined location or region within the annular space. Further, it is a problem during manufacture of the water heater device to insulate the bottom end of the water tank. Various proposals have been made to solve this problem.
U.S. Pat. No. 4,372,028 issued on Feb. 8, 1983 to Clark et al. shows a water heater having a foam-filled closed bag located in the annular space between the inner tank and outer shell at the bottom of the inner tank, with the annular space above the annular bag filled with expanded foam. The collar functions as a stop to the expanded foam in the annular space thereabove. In the manufacture of the water heater a flexible, expandable closed elongated bag having a hole therein is filled with a foam material which expands the bag, and before the foam material has had sufficient time to fully expand, the bag opening is sealed and the bag is circumferentially wrapped around the lower end of the tank with the bag ends overlapping each other. Still, before the foam material in the bag has had sufficient time to expand, the outer shell is positioned over the inner tank and bag. The foam in the bag expands to a size so as to be in compression between the inner tank and outer shell. The annular space above the collar is then filled with expandable foam material.
U.S. Pat. No. 4,447,377 issued on May 8, 1977 to Denton shows a gas-fired water heater wherein a layer of fiberglass batt insulation material is wrapped around the bottom portion of the inner water tank around the combustion chamber and a plastic envelope is wrapped around the inner tank above the fiberglass insulation. The envelope is in the form of an elongated thin tube having an inner wall, an outer wall, a bottom wall, two end walls and an open top. When wrapped around the inner tank, the end walls of the envelope abut each other. The outer shell is positioned over the inner tank such that the envelope is in the annular space therebetween. Expandable foam is injected through tthe open envelope top into the envelope and allowed to expand therein. The fiberglass batt does not form a seal between itself and the inner water tank and the outer shell.
U.S. Pat. No. 4,477,399 issued on Oct. 16, 1984 to Tilton shows a water heater having an inflatable toroidally shaped tube located around the bottom end of the inner tank such that when the toroidal tube is inflated with air, it seals the bottom end of the annular space between the inner tank and outer shell. A foamable material is then injected into the annular space above the toroidal tube to fill the annular space.
It is also known to position a layer of insulation batting, such as a layer of fiberglass batt, over the bottom end of the water tank.
Each of the above-discussed water heater constructions present numerous problems in manufacture such as, for example, a large number of steps, critically timed steps, and time-consuming steps which add to the cost and present potential for defects in the final product. In contrast, the present invention provides a simple and efficient method of constructing a hot water heater wherein the area below the tank as well as the sides of the tank are thermally insulated.